The proposed research is designed to elucidate the Escherichia coli functions which are necessary for the propagation of bacteriophage lambda, and to identify the phage gene products which interact with them. Specifically, we propose to identify, and hopefully, purify the bacterial groE gene product which is necessary for bacteriophage lambda head morphogenesis. In order to do this we have prepared a (groE) plus transducing phage. We propose to characterize and purify the two groPC bacterial genes which map between the thr and leu loci and affect bacteriophage lambda DNA replication. In order to do this we have prepared a transducing phage carrying the two groPC bacterial genes. Finally, we propose to identify the groN-B bacterial gene which maps near proC and interferes with the expression of the N gene product of bacteriophage lambda. In addition to their effect on lambda propagation all three classes of bacterial mutations interfere with bacterial growth and development. We propose to pinpoint the exact role that these genes play in bacterial growth.